This is the 486th most frequent Russian word.
первое
"Первое" - "first" or "the first."
"первое" indicates the ordinal number meaning "first" in a neuter noun context.
Первое, что я сделал утром, — это выпил кофе.
The first thing I did in the morning was having coffee.
"первое" refers to the first course of a meal, commonly a soup.
На обед я заказал первое, горячее и десерт.
For lunch, I ordered soup, a main dish, and dessert.
"первое" designates the concept of "first" in a sequential context.